In recent years, Western industrial nations have seen a steady increase in cancerous diseases, which have become one of the leading causes of death. For example, breast cancer is the most widespread cancer in women, affecting about 10% of all women in Western industrial nations.
Hitherto known methods for treating cancerous diseases aim primarily at early recognition of the disease and surgical methods or preferably selective destruction of tumor cells by chemo- or radiotherapy. These methods, however, do not permit any effective prophylaxis against the genesis of the cancerous diseases and also involve very considerable side effects.
It is further known that many kinds of cancer, including breast, ovarian, colon, lung and prostate cancer, involve an overexpression of HER-2/neu protein (also known as p185 or c-erbB2)—the protein product of the HER-2/neu oncogene. HER-2/neu protein is closely associated with a malignant and aggressive cancer phenotype. HER-2/neu protein is a transmembrane protein with a relative molecular mass of 185 kD and has a length of approximately 1255 amino acids. The amino acid sequence of HER-2/neu protein and the nucleic acid sequence of a DNA sequence encoding the HER-2/neu protein are disclosed in U.S. Pat. No. 5,869,445, which is incorporated herein by reference. The extracellular domain of HER-2/neu protein includes the peptide sequence from amino acid 1 to amino acid 675.
U.S. Pat. No. 5,869,445 discloses a method for stimulating an immune response to HER-2/neu protein in which a polypeptide having the sequence from amino acid 676 to 1255 of HER-2/neu protein is administered.
The invention is based on the finding that a vaccine comprising portions of the extracellular domain of HER-2/neu protein or functionally equivalent peptides thereof as effective components, can avoid the disadvantages of conventional cancer treatments, provide effective prophylaxis, and offer alternative to the methods of U.S. Pat. No. 5,869,445. The inventive peptides, functionally equivalent peptides thereof, conjugates and compositions permit active immunization against cancerous diseases associated with the HER-2/neu oncogene, thereby permitting prophylaxis against these cancerous diseases. In addition, the inventive peptides, functionally equivalent peptides thereof, conjugates and compositions can be used to treat an already existing cancerous disease or to accompany conventional cancer treatments. Application of the inventive peptides, functionally equivalent peptides thereof, conjugates and compositions can completely or partly avoid the considerable disadvantages associated with conventional cancer treatments.